Commercially available ion implantation systems employ an ion source that includes a source chamber spaced from an implantation chamber where one or more workpieces are treated by ions from the source. An exit opening in the source chamber allows ions to exit the source so they can be shaped, analyzed, and accelerated to form an ion beam. The ion beam is directed along an evacuated beam path to the ion implantation chamber where the ion beam strikes one or more workpieces, typically circular wafers that have been placed within the implantation chamber. The energy of the ion beam is sufficient to cause ions which strike the wafers to penetrate those wafers in the implantation chamber. In a typical application of such a system the wafers are silicon wafers and the ions are used to "dope" the wafers to create a semiconductor material. Selective implantation with the use of masks and passivation layers allows an integrated circuit to be fabricated with such a prior art implanter.
U.S. Pat. No. 4,764,394 to Conrad entitled "Method and Apparatus for Plasma Source Ion Implantation" discloses an ion implantation system for treating a target by means of ionic bombardment. Ion implantation into surfaces of a three dimensional target is achieved by forming an ionized plasma about the target within an enclosing chamber. Once the plasma is set up in a region surrounding the target, ions from the plasma are driven into the target object from all sides without need to manipulate the target. This implantation is accomplished by application of repetitive pulses of high voltage, typically 20 kilovolts or higher, that cause the ions to be driven into exposed surfaces of the target. A technique discussed in the U.S. Pat. No. '394 patent for setting up the plasma is to introduce a neutral gas into the region of the target and then ionize the gas with ionizing radiation.
The system disclosed in the U.S. Pat. No. '394 patent to Conrad sets up, by using a separate ion source, an ion plasma in a region surrounding a workpiece and then selectively pulses with negative voltage an electrode that supports the workpiece to attract the positive ions in the plasma to the workpiece. Structure and method constructed in accordance with the present invention accomplish both plasma creation and workpiece treatment with one sequence of energization pulses.